Cathode binder for sodium-ion batteries

Abstract

The present invention relates to an electrode composition for the preparation of a sodium-ion battery, comprising at least one binder and at least one active material.

Description

Technical Field

[0001] This invention generally relates to the field of energy storage in sodium-ion rechargeable secondary batteries. More specifically, this invention relates to electrode compositions for sodium-ion batteries. Background Technology

[0002] In recent years, the demand for lithium-ion batteries has increased as they are used in various electronic devices such as mobile phones and electric vehicles. However, lithium-based compounds are relatively expensive, and natural lithium resources are unevenly distributed and difficult to obtain, as they are located in only a few countries. People have been seeking alternatives to lithium. For this purpose, sodium-ion batteries have been developed. This is because sodium is very abundant and evenly distributed in the Earth's crust. Advantageously, sodium is non-toxic and more economically viable.

[0003] However, the redox potential of the Na+ / Na couple relative to the standard hydrogen electrode (SHE) is -2.71 V, which is higher than the potential of the Li+ / Li couple relative to the standard hydrogen electrode at -3.05 V, while the molar mass is three times higher. These characteristics result in lower energy density in sodium-ion batteries. Novel oxide-type cathode active materials can bridge the gap between these two technologies by improving voltage and specific capacitance. Unfortunately, these novel materials have the disadvantage of being alkaline, making them unsuitable for the binders conventionally used in solvent-based cathode manufacturing processes for lithium batteries. For example, US2024079577 discloses a sodium-ion battery comprising a cathode prepared from cathode material, PVDF, and carbon black.

[0004] However, developing sodium-ion batteries with high energy density to compete with lithium-ion batteries requires the use of oxide-type active materials with optimal energy density. Many oxide-type active materials for sodium-ion batteries are available on the market or under development, but they all exhibit high pH in water. This high pH reflects the presence of alkaline substances on the surface of the active material particles.

[0005] Therefore, there is a need for novel electrode binders that are compatible with the active materials used in sodium-ion batteries, and that enable optimal rheological properties when a coating is applied to the current collector using any coating method known to those skilled in the art.

[0006] The applicant unexpectedly discovered that the presence of compounds with acidic functional groups in a specific amount in the electrode composition enabled the manufacture of high-performance electrodes for sodium-ion batteries. Summary of the Invention

[0007] According to a first aspect, the present invention relates to a positive electrode composition for a sodium-ion battery, comprising a binder composition and at least one active material; said binder composition comprising at least one fluoropolymer P1, characterized in that, based on the entire binder composition, the total molar content of acid functional groups of said binder composition is greater than 1.40 mol.

[0008] The applicant has discovered that binder compositions with an acid functional group molar content greater than 1.40 mol% can be used to prepare high-performance electrodes for sodium-ion batteries. The binder composition may contain only the fluoropolymer P1, or a combination of the fluoropolymer P1 with an acrylic polymer P2 as defined in this application or additive C, or a mixture thereof. If the binder composition contains the fluoropolymer P1 but does not include the acrylic polymer P2 or the additive C, or a mixture thereof, then the total molar content of the acid functional groups in the binder composition corresponds to the molar content of the acid functional groups in the fluoropolymer P1.

[0009] According to a preferred embodiment, the pH of the at least one active material is greater than 12; the pH is determined according to the scheme described in this application.

[0010] According to a preferred embodiment, the at least one active material has the formula Na x M y O2; M includes at least one transition metal or a mixture of transition metals; x is between 0 and 1; y is between 0 and 1.

[0011] According to a preferred embodiment, the fluoropolymer P1 comprises repeating units derived from monomer M1a, wherein monomer M1a is selected from: vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxacyclopentene); perfluoro(2,2-dimethyl-1,3-dioxacyclopentene) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, wherein X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, wherein n is 1, 2, 3, 4, or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2Let F(CF2) be the value. p And p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propylene; or mixtures thereof.

[0012] According to a preferred embodiment, the fluoropolymer P1 comprises repeating units derived from monomer M1a and repeating units derived from monomer M1c, and optionally repeating units derived from monomer M1b; wherein monomer M1a is vinylidene fluoride; and wherein monomer M1b is selected from: vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene, tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE) and perfluoro(ethyl vinyl) ether (PE). VE) and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxane); perfluoro(2,2-dimethyl-1,3-dioxane) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CH2OCN or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, where n is 1, 2, 3, 4 or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2 Let F(CF2) be the value. p And p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene; or mixtures thereof; wherein the monomer M1c is selected from formula R 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C5 alkyl groups; R 4 Selected from -NHC(CH3)2CH2C(O)CH3 or -OR 5 , where R 5Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R 6 Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w1 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, and particularly an integer from 1 to 5; R 7 R 8 R 9 R 10 They are selected independently of each other and for each unit w1 independently from H and C1-C5 alkyl groups.

[0013] According to a preferred embodiment, the adhesive composition comprises an acrylic polymer P2, and it contains components derived from one or more of formula R. a R b C=C(R c (X) 2 ) p’ C(O)R d The repeating unit of monomer M2a, wherein the substituent R a R b and R c Independently selected from H, CO2H, and C1-C5 alkyl groups; R d Selected from -NHC(CH3)2CH2C(O)CH3 or -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R d’’ Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12Aryl or C1-C6 alkyl; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w2 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, particularly an integer from 1 to 5; R e R f R g R h They are selected independently of each other and for each unit w2 independently from H and C1-C5 alkyl groups.

[0014] According to a preferred embodiment, based on the entire binder composition, the total molar content of acid functional groups in the binder composition is greater than 1.41 mol%, advantageously greater than 1.42 mol%, preferably greater than 1.43 mol%, more preferably greater than 1.44 mol%, particularly greater than 1.45 mol%, even more particularly 1.46 mol%, suitably greater than 1.47 mol%, advantageously and suitably greater than 1.48 mol%, preferably and suitably greater than 1.49 mol%, and particularly suitably greater than 1.50 mol.

[0015] According to a preferred embodiment, the acid functional group is selected from CO2H, SO3H and PO3H2 or a mixture thereof; preferably CO2H.

[0016] According to a preferred embodiment, the binder composition comprises additive C, which includes one or more acid functional groups selected from CO2H, SO3H and PO3H2 or mixtures thereof.

[0017] According to a preferred embodiment, the electrode composition has an angle δ greater than or equal to 45°, measured at a strain level of 1%, an oscillation frequency of 1 Hz, and a temperature of 23 °C; the angle δ corresponds to the phase angle between the real part G' and the imaginary part G'' of the viscoelastic modulus.

[0018] According to a preferred embodiment, the fluoropolymer P1 comprises repeating units derived from monomer M1a as defined in this application and repeating units derived from monomer M1c as defined in this application, and has a molar content of acid functional groups greater than 1.40 mol%; preferably, monomer M1a is vinylidene fluoride, and particularly, the molar content of acid functional groups of the fluoropolymer P1 is less than 5.0 mol%.

[0019] According to a preferred embodiment, the fluoropolymer P1 is a homopolymer of vinylidene fluoride, and the adhesive composition further comprises the acrylic polymer P2 as defined in this application or the additive C as defined in this application.

[0020] According to another aspect, the present invention relates to a positive electrode comprising a current collector and a positive electrode composition according to the present invention; the positive electrode composition is deposited on at least one surface of the current collector.

[0021] According to another aspect, the present invention relates to a sodium-ion secondary battery comprising an electrode according to the present invention.

[0022] According to a preferred embodiment, the battery further comprises an electrolyte salt selected from NaCF3SO3, NaPF6, NaClO4, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2C2F5)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2C2F5), NaN(SO2CF3)(SO2C2F5), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaBETI, NaTDI, or mixtures thereof.

[0023] According to another aspect, the present invention relates to the use of fluoropolymer P1 as a binder in the preparation of a positive electrode for a sodium-ion battery; said fluoropolymer P1 has a molar content of acid functional groups greater than 1.40 mol%.

[0024] According to a preferred embodiment, the fluoropolymer P1 is as defined in this application.

[0025] According to a preferred embodiment, the acid functional group is selected from CO2H, SO3H and PO3H2 or mixtures thereof.

[0026] According to another aspect, the present invention relates to a binder composition for a positive electrode of a sodium-ion battery, comprising a fluoropolymer P1 as defined in this application, and optionally an acrylic polymer P2 as defined in this application or an additive C as defined in this application, or a mixture thereof; the binder composition having a molar content of acid functional groups greater than 1.40 mol% based on the total binder composition. Detailed Implementation

[0027] According to a first aspect of the invention, an electrode composition, particularly a positive electrode composition, is provided. The positive electrode composition comprises an adhesive composition and at least one active material. Given the alkalinity of the active material used at the cathode of a sodium-ion battery, the adhesive composition for adhering the active material to the current collector must contain a minimum amount of acidic functional groups. Therefore, based on the entire adhesive composition, the total molar content of acidic functional groups in the adhesive composition is greater than 1.40 mol%. The adhesive composition may comprise several components, each of which may provide a certain amount of acidic functional groups, up to at least 1.40 mol% in the adhesive composition. As described above, the adhesive composition preferably comprises at least one fluoropolymer P1. The adhesive composition may also comprise an acrylic polymer P2 or an additive C, or a mixture thereof. The polymer P1, the acrylic polymer P2, and the additive C are described below. Preferably, the adhesive composition consists of the fluoropolymer P1 and optionally the acrylic polymer P2 or the additive C, or a mixture thereof.

[0028] Preferably, based on the entire binder composition, the total molar content of acid functional groups in the binder composition is greater than 1.41 mol%, advantageously greater than 1.42 mol%, preferably greater than 1.43 mol%, more preferably greater than 1.44 mol%, particularly greater than 1.45 mol%, more particularly 1.46 mol%, suitably greater than 1.47 mol%, advantageously and suitably greater than 1.48 mol%, preferably and suitably greater than 1.49 mol%, particularly suitably greater than 1.50 mol%. Specifically, based on the entire binder composition, the total molar content of acid functional groups in the binder composition is greater than 1.51 mol%, advantageously greater than 1.52 mol%, preferably greater than 1.53 mol%, more preferably greater than 1.54 mol%, particularly greater than 1.55 mol%, more particularly 1.56 mol%, suitably greater than 1.57 mol%, advantageously and suitably greater than 1.58 mol%, preferably and suitably greater than 1.59 mol.

[0029] Preferably, the total molar content of acid functional groups in the adhesive composition is less than 15 mol%, advantageously less than 12 mol%, preferably less than 10 mol%, more preferably less than 8 mol%, particularly less than 5 mol%, and even more particularly less than 4 mol%.

[0030] The total molar content of acid functional groups in the adhesive composition corresponds to the sum of the molar content of acid functional groups in polymer P1 and the molar content of acid functional groups in optional polymer P2 or additive C, if the latter two are present in the adhesive composition.

[0031] Therefore, if the binder composition contains polymer P1 but not polymer P2 or additive C, the total molar content of acid functional groups in the binder composition corresponds to the molar content of acid functional groups in polymer P1. For example, if polymer P1 contains the acid functional group CO2H, the molar content of acid functional groups corresponds to the molar content of CO2H groups in polymer P1. This content is calculated using standard NMR techniques.

[0032] If the binder composition comprises polymer P1 and polymer P2, each having acid functional groups as defined in this invention, then the total molar content of acid functional groups corresponds to the sum of the molar content of acid functional groups in polymer P1 and polymer P2. Therefore, individually, polymers P1 and P2 may have a molar content of less than 1.40 mol% of acid functional groups, but the sum of their molar contents is greater than 1.40 mol%. The total molar content of acid functional groups can be determined using standard techniques such as NMR.

[0033] Fluoropolymer P1

[0034] According to a preferred embodiment, the fluoropolymer P1 contains repeating units of at least one fluorinated monomer M1a in its chain, the fluorinated monomer M1a being selected from compounds containing a vinyl group capable of being opened for polymerization and containing at least one fluorine atom, fluoroalkyl or fluoroalkoxy group directly connected to the vinyl group.

[0035] Preferably, the fluoropolymer P1 comprises repeating units derived from monomer M1a, wherein monomer M1a is selected from: vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxacyclopentene); perfluoro(2,2-dimethyl-1,3-dioxacyclopentene) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, wherein X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, wherein n is 1, 2, 3, 4, or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2 Let F(CF2) be the value. pAnd p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene; or mixtures thereof. In trifluoropropylene, 3,3,3-trifluoropropylene may be mentioned. In tetrafluoropropylene, 2,3,3,3-tetrafluoropropylene or 1,3,3,3-tetrafluoropropylene may be mentioned. In pentafluoropropylene, 1,1,3,3,3-pentafluoropropylene or 1,2,3,3,3-pentafluoropropylene may be mentioned. Chlorofluoroethylene may represent 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. 1-chloro-1-fluoroethylene isomers are preferred. Chlorotrifluoropropylene is preferably 1-chloro-3,3,3-trifluoropropylene or 2-chloro-3,3,3-trifluoropropylene.

[0036] More preferably, the fluoropolymer P1 can be a homopolymer or copolymer of monomer M1a. The comonomer of monomer M1a can be monomer M1b or monomer M1c, or a mixture thereof, as described below.

[0037] Specifically, the fluoropolymer P1 comprises at least repeating units derived from the vinylidene fluoride monomer M1a. The fluoropolymer P1 can be a homopolymer of vinylidene fluoride or a copolymer of vinylidene fluoride.

[0038] When the fluoropolymer P1 is a homopolymer of monomer M1a (e.g., vinylidene fluoride), it is preferably combined with the acrylic polymer P2 or the additive C according to the invention to form the adhesive composition according to the invention. In this case, the acrylic polymer P2 or the additive C has acid functional groups to form the adhesive composition according to the invention with an acid functional group molar content greater than 1.4 mol%.

[0039] When the fluoropolymer P1 is a copolymer of monomer M1a (e.g., vinylidene fluoride), it comprises repeating units derived from monomer M1a (e.g., vinylidene fluoride) and repeating units derived from fluorinated monomer M1b or repeating units derived from monomer M1c, or a mixture thereof. In the fluoropolymer P1, when it is the described copolymer, the mass content of repeating units derived from monomer M1a (preferably vinylidene fluoride) can be at least 50%, advantageously at least 60%, preferably greater than 70%, more preferably greater than 80%, particularly greater than 90%, and even more particularly greater than 95%.

[0040] The fluoropolymer P1 may contain repeating units derived from the fluorinated monomer M1b. The fluorinated monomer M1b is different from the monomer M1a. The fluorinated monomer M1b is preferably selected from: fluoroethylene; trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxacyclopentene); perfluoro(2,2-dimethyl-1,3-dioxacyclopentene) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, wherein X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, wherein n is 1, 2, 3, 4, or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2 Let F(CF2) be the value. p And p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene; or mixtures thereof. Preferably, the fluoropolymer P1 comprises repeating units derived from vinylidene fluoride monomer M1a and repeating units derived from fluorinated monomer M1b, said fluorinated monomer M1b being selected from: fluoroethylene; trifluoroethylene; chlorotrifluoroethylene; 1,2-difluoroethylene; tetrafluoroethylene; hexafluoropropylene; perfluoro(alkyl vinyl) ether, such as perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether or perfluoro(propyl vinyl) ether; perfluoro(1,3-dioxacyclopentene); perfluoro(2,2-dimethyl-1,3-dioxacyclopentene); formula CF2=CFO The products of the formula CF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; the products of the formula CF2=CFOCF2CF2SO2F; the products of the formula F(CF2)nCH2OCF=CF2, where n is 1, 2, 3, 4, or 5; the products of the formula R'CH2OCF=CF2, where R' is hydrogen or F(CF2)z, and z is 1, 2, 3, or 4; and the products of the formula R''OCF=CH2, where R'' is F(CF2). zAnd z is 1, 2, 3 or 4; trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene or 2-trifluoromethyl-3,3,3-trifluoro-1-propene; or mixtures thereof. Specifically, the fluoropolymer P1 comprises repeating units derived from vinylidene fluoride monomer M1a and repeating units derived from fluorinated monomer M1b, said fluorinated monomer M1b being selected from trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene and hexafluoropropylene, or mixtures thereof. Preferably, when the fluoropolymer P1 comprises said monomer M1b, based on the total weight of the fluoropolymer P1, the fluoropolymer P1 comprises 1% to 40% by weight, preferably 1% to 30% by weight, particularly 2% to 20% by weight of repeating units derived from said monomer M1b.

[0041] The fluoropolymer P1 may contain repeating units derived from monomer M1c. The monomer M1c may have acid functional groups. In this case, the monomer M1c has the formula R. 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C5 alkyl groups; R 4 Selected from -NHC(CH3)2CH2C(O)CH3 or -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R 6 Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10Alkyl hydrocarbon group; wherein w1 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, and particularly an integer from 1 to 5; R 7 R 8 R 9 R 10 The heterocycles are independently selected from H and C1-C5 alkyl groups, and for each unit w1 independently. The heterocycles can be saturated, unsaturated, or aromatic. The heterocycles can be monocyclic or bicyclic. The heterocycles can be pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, hydroxyindole, indigo, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone rings. The heterocycles can be substituted with one or more C1-C5 alkyl groups. As described above, C1-C... 18 The alkyl group may optionally be substituted with the heterocycle. The latter may be bonded to the alkyl chain via a nitrogen atom or any other atom forming the heterocycle. Preferably, the heterocycle is a 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidineone, or 4-imidazolidineone.

[0042] Advantageously, the monomer M1c has the formula R 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C5 alkyl groups; R 4 For -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R 6 Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10Alkyl hydrocarbon group; wherein w1 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, and particularly an integer from 1 to 5; R 7 R 8 R 9 R 10 They are selected independently of each other and for each unit w1 independently from H and C1-C5 alkyl groups.

[0043] Preferably, the monomer M1c has the formula R 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C5 alkyl groups; R 4 For -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C substituent 15 Alkyl; R 6 Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 10 Aryl or C1-C5 alkyl; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w1 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, and particularly an integer from 1 to 5; R 7 R 8 R 9 R 10 They are selected independently of each other and for each unit w1 independently from H and C1-C5 alkyl groups.

[0044] More preferably, the monomer M1c has the formula R 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R1 R 2 and R 3 Independently selected from H, CO2H, and C1-C3 alkyl groups; R 4 For -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C substituent 10 Alkyl; R 6 Selected from C6 aryl or C1-C5 alkyl groups optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 - and optionally a C1-C5 alkyl group with one or more -OH, -CO2H or ester groups; where w1 is an integer from 1 to 5; R 7 R 8 R 9 R 10 They are selected independently of each other and for each unit w1 independently from H and C1-C3 alkyl groups.

[0045] Specifically, the monomer M1c has the formula R 1 R 2 C=C(R 3 )(C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C3 alkyl groups; R 4 For -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C substituent 10 Alkyl; R 6 Selected from C6 aryl or C1-C5 alkyl groups optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups.

[0046] According to a particularly preferred embodiment, the monomer M1c may be acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-dodecyl acrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-dodecyl methacrylate, pentyl methacrylate, isoamyl methacrylate ... Monomers of the following formulas: hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureomethacrylate, and monomers of the formulas CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-C6H4CO2H), CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H); and mixtures thereof. Preferably, the monomer M1c has an alkyl group containing 1 to 8 carbon atoms, more preferably, the monomer M1c has an alkyl group containing 1 to 5 carbon atoms. The fluoropolymer P1 may contain one or more repeating units derived from the monomer M1c as defined herein. Preferably, when the polymer P1 contains the monomer M1c, the polymer P1 contains 0.01 wt% to 10 wt%, preferably 0.05 wt% to 5 wt%, and particularly 0.1 wt% to 5 wt% of repeating units derived from the monomer M1c, based on the total weight of the polymer P1.

[0047] Specifically, based on the total weight of the polymer P1, the fluoropolymer P1 comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, particularly at least 80% by weight, more particularly at least 90% by weight, and suitably at least 95% by weight of repeating units derived from monomer M1a (preferably vinylidene fluoride), and 0.01% to 5% by weight of repeating units derived from monomer M1c as defined above; specifically, the monomer M1c is selected from the following: acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-dodecyl acrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, methacrylic acid, methyl methacrylate, methyl methacrylate Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-dodecyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureomethacrylate, monomers of the formula CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-C6H4CO2H), CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H); and mixtures thereof.

[0048] According to another embodiment, the fluoropolymer P1 comprises repeating units derived from vinylidene fluoride monomer M1a, repeating units derived from fluorinated monomer M1b, and repeating units derived from monomer M1c; wherein monomers M1b and M1c are as defined above, for example, as defined above.

[0049] The monomer M1c can be randomly distributed in the chain of the fluoropolymer P1. Preferably, at least 50%, preferably at least 60%, of the repeating units derived from monomer M1c are randomly distributed in the chain of the fluoropolymer P1, i.e., located between two repeating units derived from monomer M1a (e.g., vinylidene fluoride).

[0050] As described above, the fluoropolymer P1 may contain acid functional groups. The acid functional groups are preferably selected from CO2H, SO3H, and PO3H2, with CO2H being the most preferred. According to a preferred embodiment, the molar content of acid functional groups in the fluoropolymer P1 is greater than 0.1 mol%, advantageously greater than 0.25 mol%, preferably greater than 0.5 mol%, more preferably greater than 0.75 mol%, and particularly greater than 1.0 mol%. Preferably, the molar content of acid functional groups in the fluoropolymer P1 is greater than 1.1 mol%, advantageously greater than 1.2 mol%, preferably greater than 1.3 mol%, more preferably greater than 1.40 mol%, particularly greater than 1.45 mol%, and even more particularly greater than 1.50 mol%. Specifically, the molar content of acid functional groups in the fluoropolymer P1 is greater than 1.51 mol, advantageously greater than 1.52 mol, preferably greater than 1.53 mol, more preferably greater than 1.54 mol, particularly greater than 1.55 mol, more particularly 1.56 mol, suitably greater than 1.57 mol, advantageously and suitably greater than 1.58 mol, preferably and suitably greater than 1.59 mol. Preferably, the molar content of acid functional groups in the fluoropolymer P1 is less than 15.0 mol, advantageously less than 12.0 mol, preferably less than 10.0 mol, more preferably less than 8.0 mol, particularly less than 5.0 mol, more particularly less than 4.5 mol, and suitably less than 4.0 mol. Specifically, the molar content of acid functional groups in the fluoropolymer P1 is between 1.4 mol% and 5.0 mol%, preferably between 1.45 mol% and 4.5 mol%; preferably, the acid functional group is CO2H.

[0051] When the molar content of acid functional groups in the fluoropolymer P1 is less than 1.4 mol%, the adhesive composition according to the present invention contains other components with acid functional groups to achieve the molar content defined in this application.

[0052] According to one embodiment, the average particle size of the polymer P1 is between 10 nm and 1000 nm. According to another embodiment, the average particle size is between 1 µm and 200 µm, preferably between 1 µm and 100 µm. The average particle size is determined by laser particle size analysis. Measurements are performed using a Malvern Insitec System type particle size analyzer. This measurement is performed by dry laser diffraction of the powder at a focal length of 100 mm.

[0053] According to some embodiments, the vinylidene fluoride contained in the fluoropolymer P1 is bio-based. The term "bio-based" means "derived from biomass." This can improve the eco-footprint of the polymer. Bio-based VDF is characterized by a renewable carbon content of at least 1 atomic percent, i.e., the content of naturally sourced carbon derived from biological materials or biomass, which is determined according to standard NF EN16640. 14 The carbon content is determined. The term "renewable carbon" indicates that the carbon is of natural origin and derived from biological materials (or biomass), as explained below. According to some embodiments, the biomass carbon content of the VDF can be greater than 5%, preferably greater than 10%, preferably greater than 25%, preferably greater than or equal to 33%, preferably greater than 50%, preferably greater than or equal to 66%, preferably greater than 75%, preferably greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99%, advantageously equal to 100%.

[0054] Preparation of polymer P1

[0055] According to a preferred embodiment, the fluoropolymer P1 is prepared by suspension polymerization or emulsion polymerization as follows to form a latex, which may optionally be dried to obtain the fluoropolymer P1 in powder form. The polymerization step uses monomer M1a as defined above, and optionally monomers M1b and / or M1c.

[0056] The polymerization step can be carried out at temperatures above 40 °C, preferably between 40 °C and 120 °C, and particularly between 40 °C and 90 °C.

[0057] The polymerization step can be carried out at a pressure of 10 bara to 120 bara, advantageously at 15 bara to 110 bara, preferably at 20 bara to 110 bara, and particularly at 40 bara to 110 bara. During the polymerization reaction, the pressure used is higher than the critical pressure of monomer M1a. In particular, when monomer M1a is vinylidene fluoride, the pressure applied during the polymerization reaction is higher than its critical pressure. The pressure can be maintained by continuously adding monomer M1a, water, or an aqueous solution of said monomer M1c.

[0058] Preferably, the monomer M1c is added to the reactor in the form of an aqueous solution. According to a preferred embodiment, the monomer M1c is added continuously to the reactor to ensure its random (uniform) distribution in the polymer P1.

[0059] The method (process) is preferably carried out in the presence of an initiator. The initiator can be one or a combination of initiators known in the art for use in the polymerization of halogenated monomer dispersions. Suitable non-limiting classes of initiators include persulfates, peroxides, and redox systems. Examples of persulfates are sodium persulfate, potassium persulfate, or ammonium persulfate. Based on the total weight of monomers added to the reaction mixture, the amount of persulfate added to the reaction mixture is typically from about 0.005 wt% to about 1.0 wt%. Available organic peroxides include dialkyl peroxides, alkyl hydroperoxides, peroxy esters, and peroxydicarbonates. A suitable example of a dialkyl peroxide is di-tert-butyl peroxide. Examples of suitable peroxy esters include tert-amyl peroxypentanoate, tert-butyl peroxypentanoate, and peroxysuccinic acid. Examples of suitable peroxydicarbonate initiators include di-n-propyl peroxydicarbonate and diisopropyl peroxydicarbonate, which are typically added to the reaction mixture in amounts from about 0.05 wt% to about 2.5 wt% based on the total weight of monomers added to the reaction mixture. The initiator may comprise a redox system. A "redox system" should be understood as a system comprising an oxidant, a reductant, and optionally a promoter as an electron transfer medium. A promoter is a component capable of reacting with both the oxidant and the reductant at different oxidation states, thereby accelerating the overall reaction. Oxidants include, for example, persulfates; peroxides, such as hydrogen peroxide; hydroperoxides, such as tert-butyl hydroperoxide and cumene hydroperoxide; and oxidizing metal salts, such as ferric sulfate and potassium permanganate. Examples of reductants include sodium formaldehyde bisulfite; sodium or potassium sulfite, sodium or potassium bisulfite, sodium or potassium metabisulfite; ascorbic acid; oxalic acid; and reduced metal salts. Typical promoters include transition metal salts, such as ferrous sulfate. In redox systems, the oxidant and reductant are typically used in amounts from about 0.01% by weight to about 0.5% by weight, based on the total weight of the monomers added to the reaction mixture. If an accelerator is used, it is typically used in amounts from about 0.005% by weight to about 0.025% by weight, based on the total weight of the monomers added to the reaction mixture.

[0060] The method can be carried out in the presence of a phase transfer agent. This phase transfer agent can be a dispersant, preferably when the method is carried out in a suspension (in a suspension manner). The dispersant can be polyvinyl alcohol (PVA) or a compound containing cellulose units, such as methylcellulose, hydroxypropyl methylcellulose, and carboxymethylcellulose. The phase transfer agent can be a surfactant, preferably when the method is carried out in an emulsion (in an emulsion manner). For example, the surfactant comprises polyethylene glycol segments and polypropylene glycol segments. Preferably, the surfactant has an HLB value of 1 to 20, particularly an HLB value of 1 to 5 or 10 to 15. Specifically, the surfactant comprising polyethylene glycol segments and polypropylene glycol segments has an HLB value of 1 to 5 and a weight-average molecular weight of 2500 to 10000 g·mol⁻¹. -1 Alternatively, the surfactant comprising polyethylene glycol and polypropylene glycol segments has an HLB value of 10 to 15 and a weight-average molecular weight of 500 to 2500 g·mol⁻¹. -1 .

[0061] Paraffinic antifouling agents can be optionally used in the polymerization. Any long-chain saturated hydrocarbon oil or wax can be used. The oil or wax is added to the reactor prior to the formation of the fluoropolymer, in an amount sufficient to minimize polymer adhesion to reactor components. This amount is typically proportional to the reactor's internal surface area and can vary from about 1 to about 40 mg / cm² of reactor internal surface area. If paraffinic wax or hydrocarbon oil is used as the antifouling agent, the amount is typically about 5 mg / cm² of reactor internal surface area.

[0062] The polymerization reaction mixture may optionally contain a buffer to maintain a controlled pH during the polymerization reaction. The pH is typically controlled within the range of 3 to 8. The buffer may be added at the start, at multiple time points, or throughout the polymerization process. Suitable buffers, as examples, are phosphate buffers and acetate buffers, which are well known to those skilled in the art.

[0063] Molecular weight modifiers (also known as chain transfer agents) can be optionally used to adjust the molecular weight distribution of the product. They can be added all at the start of the reaction, gradually, or continuously throughout the reaction. The amount of molecular weight modifier added to the polymerization reaction is typically from about 0.05% by weight to about 5% by weight, more typically from about 0.1% by weight to about 2% by weight, based on the total weight of monomers added to the reaction mixture. Oxygen-containing compounds, such as alcohols, carbonates, ketones, esters, and ethers, can be used as molecular weight modifiers. Examples of suitable oxygen-containing compounds include isopropanol, acetone, ethyl acetate, and diethyl carbonate. Other classes of molecular weight modifiers include halogenated compounds, such as chlorinated hydrocarbons, hydrochlorocarbons, hydrofluorocarbons, chlorofluorocarbons, and hydrochlorofluorocarbons. Specific examples of halogenated molecular weight modifiers include 1-fluoroethane, trichlorofluoromethane, and 1,1-dichloro-2,2,2-trifluoroethane. Certain hydrocarbons can be used as molecular weight modifiers, such as hydrocarbons containing 2 to 5 carbon atoms, with ethane and propane being specific examples.

[0064] The polymer P1 obtained at the end of the reaction can be washed and dried to form a powder. Alternatively, the polymer P1 obtained at the end of the reaction can be washed and used in latex form.

[0065] Acrylic polymer P2

[0066] The adhesive composition may further comprise an acrylic polymer P2. The presence of the acrylic polymer P2 allows for adjustment of the molar content of acid functional groups in the adhesive composition to achieve a desired threshold.

[0067] Preferably, the acrylic polymer P2 comprises one or more derivatives of formula R. a R b C=C(R c (X) 2 ) p’ C(O)R d The repeating unit of monomer M2a, wherein the substituent R a R b and R c Independently selected from H, CO2H, and C1-C5 alkyl groups; R d Selected from -NHC(CH3)2CH2C(O)CH3 or -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R d’’Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w2 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, particularly an integer from 1 to 5; R e R f R g R h The heterocycles are independently selected from H and C1-C5 alkyl groups, and for each unit w2 independently. The heterocycles can be saturated, unsaturated, or aromatic. The heterocycles can be monocyclic or bicyclic. The heterocycles can be pyrrole, pyrrolidine, pyridine, piperidine, pyrimidine, pyrazine, 1,4-dihydropyridine, indole, hydroxyindole, indigo, quinoline, isoquinoline, quinazoline, imidazoline, pyrazolidine, 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidinone, or 4-imidazolidinone rings. The heterocycles can be substituted with one or more C1-C5 alkyl groups. As described above, C1-C... 18 The alkyl group may optionally be substituted with the heterocycle. The latter may be bonded to the alkyl chain via a nitrogen atom or any other atom forming the heterocycle. Preferably, the heterocycle is a 2-pyrrolidone, δ-lactam, succinimide, 2-imidazolidineone, or 4-imidazolidineone.

[0068] Advantageously, the monomer M2a may have the formula R a R b C=C(R c (X) 2 ) p’ C(O)R d ), where the substituent R a R b and R c Independently selected from H, CO2H, and C1-C5 alkyl groups; R d For -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; Rd’’ Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w2 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, particularly an integer from 1 to 5; R e R f R g R h They are selected independently of each other and for each unit w2 independently from H and C1-C5 alkyl groups.

[0069] Preferably, the monomer M2a may have the formula R a R b C=C(R c (X) 2 ) p’ C(O)R d ), where the substituent R a R b and R c Independently selected from H, CO2H, and C1-C5 alkyl groups; R d For -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C substituent 15 Alkyl; R d’’ Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 10 Aryl or C1-C5 alkyl; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w2 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, particularly an integer from 1 to 5; Re R f R g R h They are selected independently of each other and for each unit w2 independently from H and C1-C5 alkyl groups.

[0070] More preferably, the monomer M2a may have the formula R a R b C=C(R c (X) 2 ) p’ C(O)R d ), where the substituent R a R b and R c Independently selected from H, CO2H, and C1-C3 alkyl groups; R d For -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C substituent 10 Alkyl; R d’’ Selected from C6 aryl or C1-C5 alkyl groups optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 - and optionally a C1-C5 alkyl group with one or more -OH, -CO2H or ester groups; wherein w2 is an integer from 1 to 5; R e R f R g R h They are selected independently of each other and for each unit w2 independently from H and C1-C3 alkyl groups.

[0071] Specifically, the monomer M2a may have the formula R a R b C=C(R c (X) 2 ) p’ C(O)R d ), where the substituent R a R b and R c Independently selected from H, CO2H, and C1-C3 alkyl groups; R d For -OR d’ , where Rd’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C substituent 10 Alkyl; R d’’ Selected from C6 aryl or C1-C5 alkyl groups optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups.

[0072] According to a particularly preferred embodiment, the monomer M2a may be acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-dodecyl acrylate, pentyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, diacetone acrylamide, lauryl acrylate, n-octyl acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-dodecyl methacrylate, pentyl methacrylate, isoamyl methacrylate ... Monomers of the following formulas: hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, ureomethacrylate, and monomers of the formulas CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-C6H4CO2H), CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H); and mixtures thereof. Preferably, the monomer M2a has an alkyl group containing 1 to 8 carbon atoms, more preferably, the monomer M2a has an alkyl group containing 1 to 5 carbon atoms. The acrylic polymer P2 may comprise one or more monomers M2a as defined herein.

[0073] Polymer P2 can exist as a salt or be partially salted. The salt can be a lithium salt, sodium salt, potassium salt, calcium salt, or magnesium salt.

[0074] Additive C

[0075] The binder composition may further comprise additive C. The presence of additive C allows for adjustment of the molar content of acid functional groups in the binder composition to achieve a desired threshold. Additive C is a hydrocarbon compound. Additive C includes one or more acid functional groups selected from CO2H, SO3H, and PO3H2, or mixtures thereof. Preferably, the molar mass of additive C is less than 500 g / mol. As a non-limiting example, additive C is selected from the following: tartaric acid, citric acid, oxalic acid, malonic acid, maleic acid, citraconic acid, succinic acid, adipic acid, phthalic acid, terephthalic acid, itaconic acid, acrylic acid, CH2=CH(CO2CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-CH2CH2CO2H). CH2=CH(CO2CH2CH2CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH(CH3)CH2-OC(O)-CH2CH2CO2H), CH2=CH(CO2CH2CH2-OC(O)-C6H4CO2H), and CH2=CH(CO2CH2CH2CH2CH(CO2H)CH2CH2CO2H), PSS (polystyrene sulfonic acid), polyphosphoric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentasulfonic acid, hexanesulfonic acid, dodecanesulfonic acid, p-toluenesulfonic acid, camphor-10-sulfonic acid, methanephosphonic acid, phenylphosphonic acid, octadecylphosphonic acid, and ethylphosphonic acid. Preferably, the additive C is selected from the following: tartaric acid, citric acid, oxalic acid, malonic acid, maleic acid, citracic acid, succinic acid, adipic acid, phthalic acid, terephthalic acid, itaconic acid, acrylic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentasulfonic acid, hexanesulfonic acid, dodecanesulfonic acid, p-toluenesulfonic acid, camphor-10-sulfonic acid, methanephosphonic acid, phenylphosphonic acid, octadecylphosphonic acid, and ethylphosphonic acid. Additive C may be in salt form or partially salted. The salt may be a lithium salt, sodium salt, potassium salt, calcium salt, or magnesium salt.

[0076] Active materials

[0077] As described above, the electrode composition further comprises an active material. The active material preferably has at least one pH value greater than 12. A method for measuring the pH of the active material is described below.

[0078] According to a preferred embodiment, the at least one active material has the formula Na x M yO2; M comprises at least one metal or a mixture of metals; x is between 0 and 1; y is between 0 and 1. Advantageously, M is selected from Ti, V, Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Au, Pt, Ir, Os, W, Ta, Al, Y, Ca, Li, Rb, Cs, Ce, Mo, Ba, Sc, B, and Hf. Preferably, M is selected from Cr, Mn, Fe, Mg, Co, Ni, Cu, Zn, Zr, Nb, Mo, and Hf. In particular, M is selected from Ni, Mn, Fe, Co, Cu, Zn, and Mg.

[0079] Therefore, the active materials used in the positive electrode of sodium-ion batteries are selected from the following: Na 0.95 Ni 0.317 Mn 0.317 Mg 0.158 Ti 0.208 O2, Na 0.677 Ni 0.300 Mn 0.600 Mg 0.033 Ti 0.067 O2, Na 0.68 Cu 0.34 Mn 0.66 O2, Na 7 / 9 Cu 2 / 9 Fe 1 / 9 Mn 2 / 3 O2, Na 0.90 Cu 0.22 Fe 0.30 Mn 0.48 O2, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na x MnO2, Na 0.67 Ni 1 / 3 Mn 2 / 3 O2, NaFe 0.5 Co 0.5 O2, Na x Fe 1 / 2 Mn 1 / 2 O2, Na x CrO2, NaNi 0.25 Fe 0.5 Mn 0.25 O2, Na 2 / 3 Mg 0.28 Mn 0.72 O2, Na 0.46 Co 0.5 Mn 0.5 O2, Na 0.67 Ni0.15 Fe 0.2 Mn 0.65 O2, Na x FeO2, NaFe 0.3 Ni 0.7 O2, NaLi 0.05 (Ni 0.25 Fe 0.25 Mn 0.5 ) 0.95 O2, Na 0.7 Fe 0.4 Mn 0.4 Co 0.2 O2, Na 0.97 Fe 0.5 Mn 0.5 O2, Na 0.7 (Fe 0.5 Mn 0.5 ) 0.8 Co 0.2 O2, Na x CoO2, Na x NiO2, Na 1 / 3 Ni 1 / 3 Mn 2 / 3 O2, Na 0.67 Ni 0.2 Mg 0.1 Mn 0.7 O2, Na 2 / 3 Ni 1 / 3-x Zn x Mn 2 / 3 O2, Na 0.7 Mn 0.6 Ni 0.3 Co 0.1 O2, Na 0.7 Mn 0.65 Ni 0.15 Fe 0.2 O2, Na 0.85 Li 0.17 Ni 0.21 Mn 0.64 O2, Na x TiO2, NaNi 0.5 Ti 0.5 O2, Na x VO2, Na x V2O5, Na 1+x V3O8.

[0080] Active material can be used in the battery. 1+a Ni x Mn y Fe z A mB n O2, where -0.35≤a≤0.20, 0.08<x≤0.5, 0.05≤y≤0.48, 0.03<z<0.4, 0.03<m<0.24, 0.001<n<0.06, and x+y+z+m+n=1; wherein A is selected from Ti, Zn, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P and Cu or mixtures thereof; B is selected from Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, B, F, P and Cu or mixtures thereof.

[0081] conductive agent

[0082] The electrode composition may further comprise a conductive agent. The conductive agent in the electrode is composed of one or more materials capable of improving electrical conductivity. Some examples include carbon black, such as acetylene black and Ketjen black; carbon fibers, such as carbon nanotubes, carbon nanofibers and vapor-grown carbon fibers; and metal powders, such as SUS powder and aluminum powder.

[0083] Preparation of Electrode Composition

[0084] In a preferred embodiment, the electrode composition has the following mass composition: a. 50% to 99.95%, preferably 50% to 99% of active material, b. 0% to 25%, preferably 0.5% to 25% of conductive agent, c. 0.05% to 25%, preferably 0.5% to 25% of the binder composition according to the present invention, d. 0% to 5% of at least one additive selected from plasticizers, ionic liquids, dispersants for conductive additives and glidants, The sum of all these percentages is 100%.

[0085] According to a preferred embodiment, the electrode composition has an angle δ of greater than or equal to 45°, measured at a strain level of 1%, an oscillation frequency of 1 Hz and a temperature of 23 °C; the angle δ corresponds to the phase angle between the real part G' and the imaginary part G'' of the viscoelastic modulus. When the electrode composition has a δ of greater than or equal to 45°, this enables the preparation of the electrode to be promoted by coating, that is, promoting the spreading of the electrode composition on the current collector.

[0086] According to another preferred embodiment, the electrode composition has a viscosity between 2000 cP and 7000 cP, as measured according to the scheme described below. Preferably, the viscosity of the electrode composition is between 2000 cP and 6900 cP, advantageously between 2000 cP and 6800 cP, preferably between 2000 cP and 6700 cP, more preferably between 2000 cP and 6600 cP, particularly between 2000 cP and 6500 cP, even more particularly between 2100 cP and 6500 cP, suitably between 2200 cP and 6500 cP, advantageously and suitably between 2300 cP and 6500 cP, preferably and suitably between 2400 cP and 6500 cP, and particularly suitably between 2500 cP and 6500 cP.

[0087] The electrode composition can be prepared by mixing the components (e.g., components in powder form) in desired proportions. Alternatively, the components can be mixed in the form of an aqueous solution or an organic solution (i.e., mixed in desired proportions in the presence of an organic solvent, and then the solution can be dried to obtain a powder or used directly). The organic solvent is not particularly limited, and is selected for dissolving the binder composition. Without limitation, the organic solvent can be N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), triethyl phosphite (TEP), acetone, cyclopentanone, tetrahydrofuran, methyl ethyl ketone (MEK), methyl isobutyl ketone (MiBK), ethyl acetate (EA), butyl acetate (BA), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), γ-butyrolactone, and N-butylpyrrolidone; and mixtures thereof.

[0088] The method for preparing a dry-coated electrode includes the following steps: - The active material in powder form, the binder composition according to the invention, and optionally the conductive agent in powder form, the additive in powder form, or both, are mixed to form the electrode composition according to the invention; - Depositing the electrode composition onto the current collector to fabricate an electrode; and - Optionally, the electrodes are solidified by thermomechanical treatment.

[0089] Therefore, the dry-coated electrode is prepared according to a "solvent-free" method (process), meaning that this method does not require a residual solvent evaporation step after the deposition step because all components are mixed in dry, powder form, and deposition is also carried out under solvent-free conditions. Thermomechanical treatment refers to applying mechanical pressure to the electrode at a given temperature. For example, such thermomechanical treatment can be performed using a calender containing heatable rollers or a heatable flatbed press.

[0090] As a method for solventless mixing of various components of the electrode composition prior to the stage of deposition onto the current collector, the following methods can be mentioned in an inexhaustible manner: mixing by agitation, airflow mixing, high-shear mixing, mixing with a V-type mixer, mixing with a screw mixer, double-cone mixing, drum mixing, conical mixing, double-Z-arm mixing, mixing in a fluidized bed, mixing in a planetary mixer, mixing by mechanical fusion, mixing by extrusion, mixing by calendering, and mixing by grinding.

[0091] According to one embodiment, after the powder mixing step, the electrode is manufactured by a solvent-free spraying method, namely by pneumatic spraying, by electrostatic spraying, by immersion in a fluidized powder bed, by spraying, by electrostatic screen printing, by deposition with a rotating brush, by deposition with a rotating metering roller, or by calendering, depositing the electrode composition onto a metal substrate.

[0092] According to one embodiment, after deposition onto a metal substrate by solvent-free spraying (pneumatic spraying, electrostatic spraying, immersion in a fluidized bed powder, spraying, electrostatic screen printing, deposition with a rotating brush, or deposition with a rotating metering roller), the electrode is consolidated by a calendering method. This method involves applying pressure to the electrode using two optionally heated rollers. The consolidation step is optional. Whether this step is performed depends on the technique used to deposit the components onto the electrode. Therefore, when the deposition step is performed by calendering, the consolidation step is optional because calendering allows for simultaneous deposition and consolidation of the electrode.

[0093] According to one embodiment, after the powder mixing step, the electrode is manufactured via a two-stage solvent-free process. The first step involves manufacturing a self-supporting film from the premixed formulation using a thermomechanical process (e.g., extrusion, calendering, or hot pressing). In the second step, the self-supporting film is laminated onto a metal substrate using a process combining temperature and pressure (e.g., calendering or hot pressing).

[0094] According to one embodiment, after the powder mixing step, the electrode is manufactured using a solvent-free calendering process, which allows for the film formation step and the coating transfer onto the current collector to be performed in a single step, without the need for a step of manufacturing a self-supporting film. For this purpose, the calender used has multiple rolls (at least three). The powder obtained after the mixing step is introduced between the first two rolls, which are typically heated and rotate at different speeds to shear the powder. The coating formed and held adhering to the fastest roll is then directly laminated onto the current collector using a third roll. If desired, the electrode thus obtained can then be passed through the calender again to adjust its porosity or thickness.

[0095] The resulting positive electrode comprises a current collector and a positive electrode composition according to the invention; the positive electrode composition is deposited on at least one surface of the current collector.

[0096] use

[0097] According to another aspect of the present invention, a sodium-ion battery is provided. Preferably, the sodium-ion battery comprises a positive electrode, a negative electrode, and a separator. The positive electrode is an electrode according to the present invention. Preferably, the sodium-ion battery further comprises an electrolyte salt selected from NaCF3SO3, NaPF6, NaClO4, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2C2F5)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2C2F5), NaN(SO2CF3)(SO2C2F5), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaBETI, NaTDI, or mixtures thereof.

[0098] Example

[0099] Preparation of electrode compositions

[0100] In the following examples, the adhesive compositions are copolymers of vinylidene fluoride and acrylic acid. In adhesive composition 1, the adhesive composition is Solef® 5130 (a copolymer of vinylidene fluoride and acrylic acid) containing 1 mol% acid functional groups. Adhesive compositions 2, 3, 4, and 5 are copolymers of vinylidene fluoride and acrylic acid, having 1.4 mol%, 1.5 mol%, 1.6 mol%, and 2.4 mol% acid functional groups, respectively.

[0101] The electrode composition is manufactured according to the following steps: Prepare a 7% by mass solution of the binder composition in N-methyl-2-pyrrolidone until the binder is completely dissolved. Then add Super P C65 carbon black (supplier Timcal) to the solution. Mix the solution using a mechanical stirrer. Then add Na. 0.66 Fe 0.5 Mn 0.5 O2 oxide-type active material. The pH of this active material is 12.6. N-methyl-2-pyrrolidone can then be added to adjust the final solids content. An electrode composition with a final solids content between 40% and 90% is obtained. The dry composition of the electrode composition is 96% by weight of active material, 2% by weight of binder, and 2% by weight of carbon black.

[0102] Viscosity measurement of electrode compositions applicable to metal supports

[0103] The viscosity of the electrode composition was measured at 23 °C using a TA HR 10 rheometer. The ink was placed between two parallel plates (40 mm in diameter) spaced 500 µm apart (= gap 500 µm). The viscosity was measured at 0.1 s⁻¹. -1 up to 100 s -1 Viscosity values ​​were obtained at various shear rates within a range. The table below lists the viscosity values ​​at 10 s⁻¹. -1 The value at time.

[0104] δ measurement of electrode compositions that can be applied to a metal support

[0105] The dynamic viscosity of the electrode compositions was measured at 23 °C using a TA HR 10 rheometer. The ink was placed between two parallel plates (40 mm in diameter) spaced 500 µm apart. Dynamic viscosity values ​​were obtained at various strain levels ranging from 0.1% to 100% at an oscillation frequency of 1 Hz. δ was then calculated using formulas known to those skilled in the art. The δ value at 1% was used for comparisons between various compositions.

[0106] pH measurement of active materials

[0107] The pH of the active material was measured using a potentiometric probe pre-calibrated with standards at pH 4, 7, and 10. 1 g of the active material was suspended in 10 g of demineralized water. The suspension was stirred with a magnetic stirrer for 15 min before pH reading.

[0108] The rheological properties of different electrode compositions are detailed in Table 1 below.

[0109] [Table 1]

[0110] ( (Corresponds to product Solef® 5130 / ) A value of 0 is assigned when coating is not possible on the current collector; a value of 1 is assigned when coating is possible on the current collector.

[0111] It has been found that a viscosity between 2000 cP and 7000 cP and / or a δ greater than 45° are required to obtain an electrode composition that can be properly applied to the current collector. As demonstrated in this application, binder compositions 3, 4, and 5 with a molar content of acid functional groups greater than 1.4 mol% yield optimal results and thus provide a very good trade-off for preparing uniform and high-performance electrodes. Binder compositions 1 and 2 with a molar content of acid functional groups less than 1.4 mol% produce electrode compositions (A and B) with excessively high viscosity that cannot be coated onto the current collector. Therefore, the binder compositions according to the present invention can solve the problems existing in electrode preparation in sodium-ion batteries.

Claims

1. A positive electrode composition for a sodium-ion battery, comprising a binder composition and at least one active material; said binder composition comprising at least one fluoropolymer P1, characterized in that, Based on the overall binder composition, the total molar content of acid functional groups in the binder composition is greater than 1.40 mol.

2. The positive electrode composition according to the preceding claim, characterized in that, The pH of the at least one active material is greater than 12; the pH is determined according to the scheme described in the specification.

3. The positive electrode composition according to any one of the preceding claims, characterized in that, The at least one active material has the formula Na x M y O2; M includes at least one transition metal or a mixture of transition metals; x is between 0 and 1; y is between 0 and 1.

4. The positive electrode composition according to any one of the preceding claims, characterized in that, The fluoropolymer P1 comprises repeating units derived from monomer M1a, which is selected from: vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxacyclopentene); perfluoro(2,2-dimethyl-1,3-dioxacyclopentene) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, wherein X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, wherein n is 1, 2, 3, 4, or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2 Let F(CF2) be the value. p And p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propylene; or mixtures thereof.

5. The positive electrode composition according to any one of the preceding claims, characterized in that, The fluoropolymer P1 comprises repeating units derived from monomer M1a and repeating units derived from monomer M1c, and optionally repeating units derived from monomer M1b; monomer M1a is vinylidene fluoride; monomer M1b is selected from: vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene, tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers, such as perfluoro(methyl vinyl) ether (PMVE), perfluoro(ethyl vinyl) ether (PEVE), and perfluoro... (Propylvinyl) ether (PPVE); perfluoro(1,3-dioxane); perfluoro(2,2-dimethyl-1,3-dioxane) (PDD); products of the formula CF2=CFOCF2CF(CF3)OCF2CF2X, where X is SO2F, CO2H, CH2OH, CH2OCN, or CH2OPO3H; products of the formula CF2=CFOCF2CF2SO2F; products of the formula F(CF2)nCH2OCF=CF2, where n is 1, 2, 3, 4, or 5; products of the formula R 1 The product of CH2OCF=CF2, in which R 1 It is hydrogen or F(CF2)m, and the value of m is 1, 2, 3 or 4; Equation R 2 The product of OCF=CH2, in which R 2 Let F(CF2) be the value. p And p is 1, 2, 3 or 4; perfluorobutylethylene (PFBE); trifluoropropylene, tetrafluoropropylene, hexafluoroisobutylene, pentafluoropropylene, bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoropropylene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene; or mixtures thereof; wherein the monomer M1c is selected from formula R 1 R 2 C=C(R 3 (X) 1 ) p C(O)R 4 ), where the substituent R 1 R 2 and R 3 Independently selected from H, CO2H, and C1-C5 alkyl groups; R 4 Selected from -NHC(CH3)2CH2C(O)CH3 or -OR 5 , where R 5 Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R 6 or -C(O)OR 6 C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R 6 Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p is 0 or 1; X 1 Selected from -[-C(O)OC(R) 7 (R) 8 )C(R 9 (R) 10 )-] w1 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w1 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, and particularly an integer from 1 to 5; R 7 R 8 R 9 R 10 They are selected independently of each other and for each unit w1 independently from H and C1-C5 alkyl groups.

6. The positive electrode composition according to any one of the preceding claims, characterized in that, The adhesive composition comprises an acrylic polymer P2, and it contains components derived from one or more of the formula R. a R b C=C(R c (X) 2 ) p’ C(O)R d The repeating unit of monomer M2a, wherein the substituent R a R b and R c Independently selected from H, CO2H, and C1-C5 alkyl groups; R d Selected from -NHC(CH3)2CH2C(O)CH3 or -OR d’ , where R d’ Selected from H and optionally surrounded by one or more -OH, -CO2H, -SO3H, -PO3H2, -OC(O)R d’’ or -C(O)OR d’’ C1-C groups or their ring chains containing at least one nitrogen atom are five- or ten-membered heterocyclic substituted groups. 18 Alkyl; R d’’ Selected from C6-C atoms optionally substituted with one or more -OH, -CO2H, -SO3H or -PO3H2 groups 12 Aryl or C1-C6 alkyl; p' is 0 or 1; X 2 Selected from -[-C(O)OC(R) e (R) f )C(R g (R) h )-] w2 -and optionally C1-C with one or more -OH, -CO2H or ester groups. 10 Alkyl hydrocarbon group; wherein w2 is 1 to 50, advantageously 1 to 25, preferably 1 to 10, particularly an integer from 1 to 5; R e R f R g R h They are selected independently of each other and for each unit w2 independently from H and C1-C5 alkyl groups.

7. The positive electrode composition according to any one of the preceding claims, characterized in that, Based on the overall binder composition, the total molar content of acid functional groups in the binder composition is greater than 1.41 mol, advantageously greater than 1.42 mol, preferably greater than 1.43 mol, more preferably greater than 1.44 mol, particularly greater than 1.45 mol, even more particularly 1.46 mol, suitably greater than 1.47 mol, advantageously and suitably greater than 1.48 mol, preferably and suitably greater than 1.49 mol, and particularly suitably greater than 1.50 mol.

8. The positive electrode composition according to any one of the preceding claims, characterized in that, The acid functional group is selected from CO2H, SO3H and PO3H2 or a mixture thereof; preferably CO2H.

9. The positive electrode composition according to any one of the preceding claims, characterized in that, The binder composition includes additive C, which comprises one or more acid functional groups selected from CO2H, SO3H and PO3H2 or mixtures thereof.

10. The positive electrode composition according to any one of the preceding claims, characterized in that, It has an angle δ greater than or equal to 45°, measured at a strain level of 1%, an oscillation frequency of 1 Hz, and a temperature of 23 °C; the angle δ corresponds to the phase angle between the real part G' and the imaginary part G'' of the viscoelastic modulus.

11. The positive electrode composition according to any one of the preceding claims, characterized in that, The fluoropolymer P1 comprises repeating units derived from monomer M1a as defined in claim 4 and repeating units derived from monomer M1c as defined in claim 5, and has a molar content of acid functional groups greater than 1.40 mol%; preferably, monomer M1a is vinylidene fluoride, and particularly, the molar content of acid functional groups of the fluoropolymer P1 is less than 5.0 mol%.

12. The positive electrode composition according to any one of claims 1 to 10, characterized in that, The fluoropolymer P1 is a homopolymer of vinylidene fluoride, and the adhesive composition further comprises the acrylic polymer P2 as defined in claim 6 or the additive C as defined in claim 9.

13. A positive electrode comprising a current collector and a positive electrode composition according to any one of the preceding claims; said positive electrode composition is deposited on at least one surface of said current collector.

14. A sodium-ion secondary battery comprising the electrode according to the preceding claims.

15. The battery according to claim 14, characterized in that, It also contains electrolyte salts selected from NaCF3SO3, NaPF6, NaClO4, NaBF4, NaB(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F3)2, NaN(SO2C2F5)2, NaN(SO2F)(SO2CF3), NaN(SO2F)(SO2C2F5), NaN(SO2CF3)(SO2C2F5), NaAsF6, NaBF2C2O4, NaNO3, NaPF3(CF2CF3)3, NaBETI, NaTDI, or mixtures thereof.

16. Use of fluoropolymer P1 as a binder in the preparation of the positive electrode of a sodium-ion battery; wherein the fluoropolymer P1 has a molar content of acid functional groups greater than 1.40 mol%.

17. The use according to the preceding claims, characterized in that, The fluoropolymer P1 is as defined in claim 4, 5 or 11.

18. The use according to any one of claims 16 or 17, characterized in that, The acid functional group is selected from CO2H, SO3H and PO3H2 or mixtures thereof.

19. A binder composition for a positive electrode of a sodium-ion battery, comprising a fluoropolymer P1 as defined in claim 4, claim 5, or claim 11, and optionally an acrylic polymer P2 as defined in claim 6 or an additive C as defined in claim 9, or a mixture thereof; the binder composition having a molar content of acid functional groups greater than 1.40 mol% based on the total binder composition.

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